Update link in deleting the files

[codewithdev]

Closing #838

What thing being changed:

The documentation for "Deleting the files" contains invalid URL. This can be fixed by changing the URL from https://YOUR.PARSE-SERVER.HERE/parse/files/...profile.png to https://YOUR.PARSE-SERVER.HERE/parse/files/profile.png

[mtrezza]

Thanks for this PR! Could you incorporate an explanation, as described in the issue?

The documentation can be improved quickly by adding a clear example to explain how to format the URL.

For example :

Although the file's URL is 'http:////YOUR.PARSE-SERVER.HERE/parse/files/appId/my_picture.png', you have to remove the '/appId' section from the URL to access the API endpoind.

So the URL must be : 'http:////YOUR.PARSE-SERVER.HERE/parse/files/my_picture.png'

Otherwise it will not work.

[codewithdev]

Definitely! The images are located in the directory of parse which is /files and whenever send DELETE request to the given URL( https://YOUR.PARSE-SERVER.HERE/parse/files/...profile.png) which is an invalid format of the URL. Although, "appId" is required to retrieve the images which needs to be deleted.

[mtrezza]

Yes, I think a short explanation that appId is required for retrieving but not deleting would be good in the docs. As I read the original issue, that missing info created the difficulty.